Inorganic SnIP-type double helices: promising candidates for high-efficiency photovoltaic cells

Abstract

Unique structures often come with unique properties. Recently synthesized SnIP, the first inorganic atomic-scale double helical quasi-1D semiconductor, possesses unique mechanical, electronic and optical properties including high flexibility, remarkable electron mobility, and excellent ferroelectricity, making it a promising material for flexible semiconductor devices and mechanical sensors. Inspired by the distinctive structure and properties of SnIP, here we conduct comprehensive theoretical studies on this novel class of SnIP-type double helices, denoted as XYPn (X = Si, Ge, Sn; Y = Cl, Br, I; Pn = P, As), using first-principles calculations with the focus on investigating their fundamental properties for photovoltaic applications. By carefully considering reasonable criteria such as suitable bandgaps, thermodynamic stabilities, and high theoretical limits of photovoltaic efficiencies, we identify SnIAs as the most promising candidate for high-efficiency photovoltaic solar cells. We predict that SnIAs exhibits an absorption coefficient exceeding 10⁵ cm⁻¹ in the visible light region and a quasi-direct bandgap of 1.56 eV according to the HSE06 calculations. Importantly, we predict an excellent spectroscopic limited maximum efficiency (SLME) of 30% for SnIAs, surpassing the performance of the widely studied organic–inorganic hybrid lead halide perovskite CH₃NH₃PbI₃. Further analysis indicates the existence of stable chemical potential regions for SnIAs, suggesting its high likelihood of successful synthesis in experiments. Our work unravels the potential of SnIP-type double helical semiconductors for high-efficiency photovoltaic solar cells.